It's tasklist and taskkill. It's in the \windows\system32 as tasklist.exe and taskkill.exe for Windows XP Pro and I assume 2003 server. You can copy these file to XP Home because Home doesn't have them to the same directory.

2000 Pro has tlist.exe and kill.exe, which you have to get from the CD-ROM support tools or download from here Must-Have Utilities and put it in the winnt\system32 folder.